1. Field of the Invention
The present invention relates to a production method of primary amines by the catalytic hydrogenation of nitrites and a catalyst for use in the production.
2. Description of the Prior Art
The production of primary amines by the hydrogenation of nitrites in the presence of a hydrogenation catalyst containing a metal selected from nickel, cobalt and iron have been well known. In the production of primary amines by the hydrogenation of nitrile, condensation products such as secondary and tertiary amines are by-produced by the intermolecular condensation, to reduce the yield of primary amines (Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis, Shigeo Nishimura, John Wiley&Sons, Inc., Chapter 7 Hydrogenation of Nitriles p 254-285).
To prevent the by-production of secondary and tertiary amines by the condensation, a method where the hydrogenation is conducted in ammonia solvent (JP 53-20969B, JP 8-299799A, JP 2002-505192A and JP 51-6971A) and a method where the hydrogenation is conducted in the presence of a hydroxide of an alkali metal or alkaline earth metal (JP 7-518900A, JP 7-517801A, JP 38-8719B and JP 54-41804A) have been hitherto well known. However, the use of ammonia solvent requires a pressure-resistant apparatus because of a high vapor pressure of ammonia. The industrial use of alkali metal involves a difficulty in the treatment of waste liquid containing alkali metal. In addition, these method are difficult to completely prevent the side reaction. Therefore, the improvement is still required.
To prevent the side reaction thereby to increase the yield, there have been proposed a method to modify the catalyst with formaldehyde, etc. in a liquid dispersion medium (JP 2001-212461A), a method of carrying out the hydrogenation in the co-presence of a cyanate (JP 2001-302595A), and a method of carrying out the hydrogenation in the presence of an alkali carbonate-modified catalyst which is prepared by treating the catalyst in an aqueous solution of alkali carbonate (US 2005/0159624A). These methods are reported to be used in combination with the hydrogenation in ammonia solvent or the hydrogenation in the co-presence of an alkali metal or alkaline earth metal, and proved to improve the yield in some extent. However, the method of modifying the catalyst with formaldehyde and the method of using the alkali carbonate-modified catalyst need an additional step of pretreating the catalyst in an aqueous solution. If the hydrogenation is conducted in a non-aqueous solvent, the water should be removed from the catalyst by repeated solvent exchange operation, to complicate the process. The method of using the cyanate is not industrially advantageous because the cyanate is an expensive and special chemical. In JP 40-10133B and Japanese Patent 2937083, a method of selectively hydrogenating one of two nitrite groups in the presence of a catalyst pretreated with carbon monoxide, etc. is proposed. However, these patent documents address or consider nothing about the reduction of yield in the hydrogenation of nitrites which is caused by the side reaction. In addition, these patent documents are completely silent about the hydrogenation of two nitrile groups and address or consider nothing about the problems involved in the hydrogenation of two nitrile groups.
In any of the known methods, it is difficult to completely prevent the side reaction which by-produces the condensation products. Therefore, it is keenly required to develop an improved method which is capable of preventing the side reaction to increase the yields.